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      11-21-2012, 08:39 PM   #1
ArtE36M3
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Problem with DCT

I have put just over 2500 miles on my m5 and have noticed that sometimes it gets stuck in 2nd gear when coming to a stop. It doesn't automatically go to 1st. This has happened a few times. It is an inconsistent problem. I drive most of the time during my commute in comfort and efficiency settings with the DCT in D1 mode. I notice that it usually gets triggered if I come to a slow stop during traffic. It won't down shift to first even if I come to a complete stop after that. When I accelerate from a stop stuck in 2nd it will not downshift even if my mash on the throttle. This will continue for awhile until I pick up enough speed to at least get into 4th or 5th gear then it is fine at the next complete stop. If I try to reproduce this I can't. Anyone else experience this? I am wrong to assume that the DCT should automatically go into 1st if I come to a complete stop? I noticed this first when I was in Germany during my pick up but hasnt been that consistent.
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      11-21-2012, 09:09 PM   #2
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I think thats normal and shifts the same way in my car too...
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      11-21-2012, 09:11 PM   #3
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Interesting.... I have a 6MT and have had issues with second gear... BMW is set to replace my transmission as soon as they can get one...


I have been thinking of my drivetrain choice as the problem but maybe its not...


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      11-21-2012, 09:18 PM   #4
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As far as I know the 'D1' drivelogic setting should start your off in 2nd most of them time (I have to confess that I dont drive in D1 myself and my reference is from the DCT on the M3), especially if the transmission is expecting your next start to be slow. I think part of the inconsistancy youre seeing may be your driving style confusing the DCT. From what I remember, the DCT does have some level of adaptive programming built in. It doesnt generally expect an accelerator mash from stand still in 'D1', but, if you do it once, it might go down to 1st the next time you stop thinking you may do it again. As far as shifting down from 2->1 during hard acceleration, I would figure it doesnt do that in order to avoid heavy wear on the odd numbered clutch (and there would be insane pressure on the clutch plate if you tried to shift down in the big gears while pulling a ton of torque from the engine) or to avoid a safety issue with the rev limiter. The DCT behaviour will also vary with operating temperature. If the transmission is either too cold or too hot (cant remember which one) it wont start from 2nd even in 'D1'.

As far as the efficiency settings go, always take them with a grain of salt. The driving style will impact fuel consumption much more than the drivelogic setting. If you intend on accelerating fast, you may actually burn more fuel in 'D1' than a more aggressive setting simply because the shift points may result in the acceleration taking longer.

So, I think the behaviour youre seeing may just be the intended behaviour of the transmission, but, a lot of this is speculation and someone in the know may be able to fill the both of us in better.
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      11-21-2012, 09:35 PM   #5
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Quote:
Originally Posted by ArtE36M3 View Post
I have put just over 2500 miles on my m5 and have noticed that sometimes it gets stuck in 2nd gear when coming to a stop. It doesn't automatically go to 1st. This has happened a few times. It is an inconsistent problem. I drive most of the time during my commute in comfort and efficiency settings with the DCT in D1 mode. I notice that it usually gets triggered if I come to a slow stop during traffic. It won't down shift to first even if I come to a complete stop after that. When I accelerate from a stop stuck in 2nd it will not downshift even if my mash on the throttle. This will continue for awhile until I pick up enough speed to at least get into 4th or 5th gear then it is fine at the next complete stop. If I try to reproduce this I can't. Anyone else experience this? I am wrong to assume that the DCT should automatically go into 1st if I come to a complete stop? I noticed this first when I was in Germany during my pick up but hasnt been that consistent.
My M6 does the same thing it's cause your engine setting is in efficient put it to sport and it won't do it anymore.
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      11-21-2012, 10:07 PM   #6
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I've had it twice on My car. Both times in D1 / Efficient. Thought it felt a little strange.
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      11-21-2012, 10:23 PM   #7
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Mine does the same thing. E92 M3 does as well. I try not to shift into 1st only because of the jarring deceleration. Most of the time the car won't shift into 1st on it's own. Why, I couldn't tell you. But, to my knowledge, it sounds like your car is operating normally. Not sure if the jarring effect is from Efficient Dynamics kicking in. Or just the way the engineers tried to make the deceleration a bit more comfortable for us. My approach to most anomalies in BMW's is to let the dealership know that something is odd. Then drive the car until something breaks. Most of the time nothing is wrong with the car. And, undergoing a transmission change would make me want to trade the car in. If it still operates normally in every other respect, I would say you're in good shape. Just my opinion.
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      11-22-2012, 12:29 AM   #8
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It is a normal part of the DCT in D1. Mine does it regularly in stop start traffic. If it gets annoying I just flick it into manual and leave it in 1st for a while.
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      11-22-2012, 12:39 AM   #9
ArtE36M3
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Thanks for the responses. I probably wouldn't of made it an issue with the service department at risk of needing major surgery to correct unless the problem got worse. I guess its normal. But I think it's weird to have programmed the DCT this way. Does this put more stress on the clutch starting from 2nd that often?
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      11-22-2012, 04:13 AM   #10
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It is the way is intended to be, it's completely normal. When driving in Comfort it will be in 2, if you switch to Sport or Sport+ you will always go to 1. You have plenty of power in 2 gear so no need to pull of in 1st gear....
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      11-22-2012, 04:44 AM   #11
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Quote:
Originally Posted by ArtE36M3 View Post
Thanks for the responses. I probably wouldn't of made it an issue with the service department at risk of needing major surgery to correct unless the problem got worse. I guess its normal. But I think it's weird to have programmed the DCT this way. Does this put more stress on the clutch starting from 2nd that often?
Technically, yes, it will cause more clutch wear to start in second because less power to the wheels will require a slower engage time on the clutch which increases the asynchronous contact time on the plate. Practically, however, it doesnt make a difference for two reasons. First, this car has so much power that the increase in clutch slippage due to starting in 2nd will be marginal at best. Second, the DCT is designed to handle much more wear on the clutch plates than a conventional manual transmission (it also has more plates). In order to prevent power dropout while shifting, both the clutch plates for the incoming and outgoing gears are required to slip (in a conventional transmission there would be very little slip when dissengaging a gear) and one would expect that the increased wear would be expected and handled in the transmission design.

Long story short, if you like the extra smoothness or comfort of starting in 2nd, keep doing it because it probably wont do anything to hurt the car.
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      11-22-2012, 05:31 AM   #12
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Mine also tends to stay in 2nd when in D1 (but not always) and driving in slow traffic. I always switch to manual when this happens, knocking it down to 1st, then switch back to D1 (if I want to keep it in auto).
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